Microbial activity on the microstructure of bacteria modified mortar

Microbial modified mortar or concrete has become an important area of research for high-performance construction materials. This study investigates the effects of incorporating a facultative anaerobic hot spring bacterium on the microstructure of a cement–sand mortar. Environmental scanning electron microscopic (ESEM) views and image analysis (IA) of the bacteria modified mortar (thin-section) showed significant textural differences with respect to the control (without bacteria) samples. X-ray diffraction (XRD) study confirmed the formation of new phases of silicates (Gehlenite) within the matrix of such mortar material, which causes an improvement in the strength of the material. Electron probe microstructure analysis (EPMA) suggested that the bacterial treatment promoted uniform distribution of silicate phases and increased the calcium/silicon ratio within CSH gel of the matrices. The bacterium is found to leach a novel protein, which is capable of isolating silica from its source. The addition of such isolated protein, instead of the bacteria, into mortar also improves the strength of mortar.